Tissue dilation system and methods of use

ABSTRACT

Disclosed herein are systems and methods for dilating tissue for placement of a pedicle screw without the use of guide wires. The tissue dilation system includes, generally, a stylet and trocar which are used for the initial placement of the tissue dilation system. A second dilator is passed over the first. A second dilator is passed over the first dilator, and further includes a serrated edge for engaging with a target surface. The second dilator may be secured to the target surface by the serrated edge alone, or may additional be secured using one or more temporary fixation pins, which operably couple to the second dilator.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.16/071,033, filed on Jul. 18, 2018 as a national stage entry ofInternational Application No. PCT/US2017/014068, filed on Jan. 19, 2017,which claims priority to, and the benefit of, U.S. ProvisionalApplication Ser. No. 62/280,198 which was filed on Jan. 19, 2016, theentire contents of each of which are incorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates to surgical dilation systems. Moreparticularly, the present disclosure relates to a tissue dilation systemand methods of use.

BACKGROUND

Development of minimally invasive surgical techniques has expanded toimprove orthopedic surgical techniques. Such techniques have advancedthe improvement of spinal surgeries, such as instrumental fusionsinvolving one or more vertebral bodies. Unlike minimally invasiveprocedures which focus on smaller regions of the body, such asarthroscopic knee surgery or gallbladder surgery, spinal fusion surgerycan encompass a considerable region of the body.

The spinal column is a complex system of bones and connective tissuesthat provide support for the human body and protection for the spinalcord and nerves. The adult spinal column is comprised of an upper andlower portion. The upper portion contains twenty-four discrete bones,which are subdivided into three areas including seven cervicalvertebrae, twelve thoracic vertebrae and five lumbar vertebrae. Thelower portion is comprised of the sacral and coccygeal bones. Thecylindrical shaped bones, called vertebral bodies, progressivelyincrease in size from the upper portion downwards to the lower portion.

Minimally-invasive surgery, including arthroscopic surgery andlaparoscopic surgery allow for the introduction of fluid (such asliquids or pressurized gasses) for distending tissue and creatingworking space for the surgeon to operate within. Spinal column surgerydoes not involve distending tissue to create a cavity in which thesurgeon can operate, rather, spinal column surgery often involvesinteracting with multiple layers of soft tissue, ligaments, nerves, andultimately bone. For these reasons, the idea of performing minimallyinvasive orthopedic surgeries has been the focus of many recent medicaladvances.

Minimally-invasive surgery techniques associated with orthopedic surgeryoften required a surgeon insert a guide wire through tissue toward apedicle of the vertebral body. The guide wire thereby enabled thesurgeon to accurately attach a pedicle screw to the vertebral body tolater secure a rail or rod to the vertebral body. However, duringinstallation, the guide wire may not be inserted to a sufficient depthin the vertebral body, resulting in detachment of the guide wire fromthe vertebral body prior to insertion of the pedicle screw.Disengagement of the guide wire may result in contamination andnecessitate replacement of the guide wire. Additionally, a guide wiremay deflect or break during the surgical procedure as a result ofcatching on a foreign object such as a surgeon's clothing. As a resultof deflecting or breaking guide wires, the surgical procedure isprolonged as replacements are fitted as is necessary.

As a result, procedures or surgical instrument improvements associatedwith guiding pedicle screws to vertebral bodies are desirable.

SUMMARY

The present disclosure relates to a tissue dilation system including atrocar having an elongated body with a bore extending therethrough. Adistal region of the elongated body has threads for engaging bone. Astylet is insertable into the bore. The system further includes a firstdilator having an elongated body and translatable over an outer surfaceof the trocar, and an outer dilator having an elongated body andtranslatable over an outer surface of the first dilator.

The tissue dilation system may further include a handle portionconfigured to be removably attached to the trocar.

The handle portion may be configured to be removably attached to thefirst dilator.

The tissue dilation system may further have at least one temporaryfixation pin with an elongated body and being translatable along anouter surface of the outer dilator. The temporary fixation pin may havea threaded distal region for engagement with bone.

The outer dilator may be configured to receive a surgical device to betranslated within the outer dilator for engaging bone.

A retractor assembly having a retractor and a screw inserter assemblymay also be provided.

The retractor assembly may further include a screw and a knob.

The present disclosure also provides a method for dilating tissueincluding inserting a trocar into a target surface. The trocar has atubular member with a bore extending between proximal and distal regionsthereof. The distal region includes threads for engaging bone. Themethod further includes coupling a stylet to the trocar such that adistal region of the stylet extends beyond the distal region of thetrocar. Bone is contacted at the target surface with the distal regionof the trocar. The stylet is separated from the trocar by translating afirst dilator over the trocar towards bone at the target surface andtranslating an outer dilator over the first dilator. The outer dilatoris then coupled to bone at the target surface.

The method for dilating tissue may include connecting the trocar withbone at the target surface.

Translating the first dilator over the trocar may include the firstdilator having a serrated edge configured to engage with a targetsurface.

Translating the outer dilator over the first dilator may include theouter dilator having a distal region with a serrated edge configured toengage with a target surface.

Translating the first dilator over the trocar may include the firstdilator having a bore configured for slidably receiving the trocar.

Translating the outer dilator over the first dilator may include theouter dilator having a bore configured to engage with an outer surfaceof the first dilator.

The method for dilating tissue may include removably attaching a handleto either the trocar or the first dilator.

The method for dilating tissue may include coupling the first dilatorand the outer dilator prior to translating the first dilator over thetrocar towards bone at the target surface.

The method for dilating tissue may include coupling the outer dilator tobone at the target surface by coupling a temporary fixation pin to boneat the target surface, the temporary fixation pin in communication withthe outer dilator and having a threaded distal region configured toengage with the target surface.

The method for dilating tissue may include separating the trocar fromthe target surface.

The method for dilating tissue may include separating the first dilatorfrom the target surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate embodiments of the tissue dilationsystem of the present disclosure.

FIG. 1 is a perspective view of a trocar for use in a tissue dilationsystem;

FIG. 2 is a front plan view of the trocar illustrated in FIG. 1 ;

FIG. 3 is a cross-sectional view of the trocar of FIG. 2 as taken alongsection line 3-3 of FIG. 2 ;

FIG. 4 is a perspective view of the trocar of FIG. 1 attached to ahandle portion;

FIG. 5 is a front plan view of the trocar and handle portion of FIG. 4 ;

FIG. 6 is a cross-sectional view of the trocar and handle portion ofFIG. 5 taken along section line 6-6 of FIG. 5 ;

FIG. 7 is a perspective view of a tissue dilation system according tothe present disclosure;

FIG. 8 is a plan view of the tissue dilation system of FIG. 7 ;

FIG. 9 is a cross-sectional view of the tissue dilation system of FIG. 8as taken along section line 9-9 of FIG. 8 ;

FIG. 10 is a perspective view of the trocar of FIG. 1 and a firstdilator according to the present disclosure;

FIG. 11 is enlarged view of the area of detail of FIG. 10 ;

FIG. 12 is a front plan view of the trocar and first dilator of FIG. 10;

FIG. 13 is a cross-sectional view of the trocar and first dilator ofFIG. 12 taken along section line 13-13 of FIG. 12 ;

FIG. 14 is an exploded view, with parts separated, of an alternateembodiment of a tissue dilation system according to the presentdisclosure;

FIG. 15 is a perspective view of a further embodiment of a tissuedilation system according to the present disclosure;

FIG. 16 is an exploded view, with parts separated, of the tissuedilation system of FIG. 15 ;

FIG. 17 is a side elevation view of the tissue dilation system of FIG.15 ;

FIG. 18 is a cross-sectional view of the tissue dilation system of FIG.17 taken along section line 18-18 of FIG. 17 ;

FIG. 19 is an enlarged view of the area of detail of FIG. 18 ;

FIG. 20 is an enlarged view of the area of detail of FIG. 18 ;

FIG. 21 is a perspective view of a retractor collar;

FIG. 22 is a perspective view of an outer dilator;

FIG. 23A is a front plan view of the outer dilator of FIG. 22 ;

FIG. 23B is a side plan of the outer dilator of FIG. 22 ;

FIG. 24 is a cross-sectional view of the outer dilator of FIG. 23B,taken along section line 24-24 of FIG. 23B;

FIG. 25A is a top plan view of the outer dilator of FIG. 22 ;

FIG. 25B is a bottom plan view of the outer dilator of FIG. 23B;

FIG. 26A is a side plan view of a temporary fastener;

FIG. 26B is a top view of the temporary fastener of FIG. 26A; and

FIG. 27 is a front plan view of another embodiment of an outer dilatorand the temporary fastener of FIG. 26A.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described in detail withreference to the drawings, in which like reference numerals designateidentical or corresponding elements in each of the several views.

As used herein, the term “distal” refers to the portion of the componentbeing described which is closer to a patient, while the term “proximal”refers to the portion of the component being described which is fartherfrom the patient.

The term “clinician” as used herein refers to a doctor, nurse,healthcare provider which may include support personnel, or otheroperators of the surgical system described.

Additionally, the positional terms “front,” “rear,” “top,” “bottom,”“side,” and other like directional terms are used for convenience toassist the reader in understanding the present disclosure, and are notintended to limit the disclosure.

Referring initially to FIG. 1 , a trocar 100 is shown including aproximal region 104, a tubular member 106, and a distal region 116. Theproximal region 104 includes a proximal end 102 which may be operablycoupled to a stylet 300 (see FIGS. 4-6 ). The proximal region 104 of thetrocar 100 may further be dimensioned to receive a handle portion 200thereon, (see FIG. 4 ) or other surgical tools (not shown) useful for adilation procedure.

The tubular member 106 of the trocar 100 extends between the proximalregion 104 and the distal region 116 of the trocar 100. The tubularmember 106 may be configured and dimensioned for atraumatic advancementthrough tissue along a longitudinal axis A-A as the trocar 100 isadvanced by a clinician toward a target surface (not shown). Likewise,the distal region 116 of the trocar 100 includes a tapered surface 108located between the tubular member 106 and an engagement member 112 forpromotion of atraumatic advancement of the trocar 100 through tissue andoperative engagement with an inner dilator 400 (see FIG. 7 ). Theengagement member 112 may include a helical thread, barb, expanding lip,rotated or expanded cam, and other such shaped elements disposed on theouter surface 112A (see FIG. 3 ) of the engagement member to secure thetrocar 100 to the target surface. The engagement member 112 furtherincludes an engagement tip 114 which may include a single ormulti-beveled tip for easy viewing via a sub-dermal imaging system asthe trocar 100 is advanced toward a target surface.

Referring now to FIGS. 2-3 , the trocar 100 includes a bore 118 whichextends through the trocar 100 along the longitudinal axis A-A. The bore118 is dimensioned to slidably receive a stylet 300 (see FIG. 6 )therein for selective engagement of the target surface by either adistal tip 308 of the stylet 300 or the engagement tip 114 (see FIG. 6). The bore 118 may be dimensionally defined by an inner surface of thetrocar 100.

Referring now to FIGS. 4-6 , the trocar 100 is shown in combination witha handle portion 200 and a stylet 300. The handle portion 200 includes ahandle member 202 which is capable of being gripped by a clinician'shand. The handle portion 200 may further include an extension 206 withone or more flanges 204 disposed thereon for engagement by a clinicianabout the longitudinal axis A-A during assembly and removal of thehandle portion 200 from the trocar 100. An engagement surface 208 may belocated in the distal region of the handle portion 200, defining acavity 212 therein. The cavity 212 may be dimensioned to fixably receivethe proximal region 104 of the trocar 100. Additionally, the cavity 212and the proximal region 104 of the trocar 100 may be dimensioned totransfer rotational or torsional force from the handle portion 200 tothe trocar 100. The cavity 212 and proximal region 104 of the trocar maybe shaped in a variety of ways, including two or more sided shapes,asymmetrical shapes, or patterned shapes that are complementary suchthat cavity 212 is rotatably coupled with the proximal region 104 andremovably coupled to the trocar 100.

With continued reference to FIGS. 4-6 , the handle portion 200 andtrocar 100 may be combined with a stylet 300. The stylet 300 includes aknob 302 having a knurled surface which may be gripped by a clinician.The knob 302 may further include threads 304 which operably engagethreads 210 of the handle portion 200 for releasably coupling the stylet300 and the handle portion 200. The stylet 300 further includes a shaft306 extending from the knob 302, with the shaft 306 being configured anddimensioned for slidably engaging the bore 118 of the trocar 100.Further still, the shaft 306 may be dimensioned such that when thestylet 300 is threadably coupled with the handle portion 200, the distaltip 308 of the shaft 306 extends beyond a distal end of the engagementtip 114 of the trocar 100.

Handle portion 200 may engage with trocar 100 via a spring collet (notshown). In the fixed position, the spring collet associated with handleportion 200 includes ball bearings which are located between the handleportion 200 and the trocar 100. The ball bearings apply pressure againstthe trocar 100, thereby maintaining the position of the handle portion200 relative to the trocar 100. To remove the handle portion 200, theclinician applies upward force (i.e., proximal movement) to the handleportion 202 relative to the flanges 204. By pulling the handle portion202 proximally relative to the flanges 204, the pressure applied to theball bearings is reduced, thereby allowing the clinician to remove thehandle 200. The handle 200 is releasably coupled with the trocar 100 byreleasing the handle portion 202, thereby applying pressure against theball bearings and trocar 100. Alternatively, it is contemplated that thereverse arrangement may be employed where proximal movement of theflanges 204 relative to the handle portion 202 release pressure againstthe ball bearings allowing the handle 200 to be separated from thetrocar 100.

Referring now to FIGS. 7-9 , a tissue dilation system “D” is shown withthe trocar 100, the handle portion 200, an inner dilator 400, and anouter dilator 500. As shown, in combination, the handle portion 200attaches to the trocar 100. When the handle portion 200 is removed fromthe trocar 100, the inner dilator 400 may be passed over the trocar 100,and the outer dilator 500 may be passed over the inner dilator 400. Theinner dilator 400 may be dimensioned to selectively engage with thetrocar 100 or the outer dilator 500 during assembly of the tissuedilation system “D” during a surgical dilation procedure.

With additional reference to FIG. 10 , the inner dilator 400 includes areceiving portion 402, a tubular member 404, a tapered surface 406, anda bore 408 (see FIG. 13 ). The receiving portion 402 may be dimensionedto engage with a surgical tool (not shown) during the dilationprocedure, the surgical tool permitting the clinician to apply forcedistally against the inner dilator 400. Engagement of the receivingportion 402 with the surgical tool assists the clinician while advancinginner dilator 400 through tissue where the application of additionaldistal force is desired. The tubular member 404 extends between aproximal and distal region of the inner dilator 400 along longitudinalaxis A-A defining the bore 408 therethrough. The tubular member 404further includes a tapered surface 406 located in the distal region ofthe inner dilator 400 for atraumatically displacing tissue while theinner dilator 400 is advanced toward the target surface.

With continued reference to FIGS. 7-9 , the outer dilator 500 includestwo flanges 502 for a clinician to grip during the dilation procedure.The flanges 502 extend from the tubular member 504 of the outer dilator500 in the proximal region of the tubular member 504. The tubular member504 may have one or more openings 510 located thereon, allowing aclinician to view a bore 518 defined through the tubular member 504. Thebore 518 of the outer dilator 500 is dimensioned to permit the outerdilator 500 to be passed over the inner dilator 400 such that the innerdilator 400 extends therethrough. Further, a clinician can view theprogression of the outer dilator 500 over the inner dilator 400 throughthe one or more openings 510 of the outer dilator 500.

Both the inner dilator 400 and the outer dilator 500 include taperedsurfaces 406, 506 dimensioned to minimize unintentional engagement oftissue surrounding or located at the target surface by a clinicianduring the dilation procedure. The tapered surface 406, 506 of both theinner dilator 400 and outer dilator 500 gradually displace tissue as theinner dilator 400 or outer dilator 500 is advanced through tissue duringthe dilation procedure toward the target surface.

The outer dilator 500 may further include a serrated edge 508 located onthe distal end of the outer dilator 500. The serrated edge 508 providesa surface for rigid connection with bone or other target tissue along atarget surface. By including serrated edge 508, outer dilator 500 may bepositioned relative to the bone or other target tissue with or withoutadditionally securing the outer dilator 500 to the target surface priorto advancement of a retractor assembly 600 through the outer dilator500.

With reference to FIG. 9 , the cross-section of tissue dilation system“D” shows, in combination, the trocar 100, inner dilator 400, outerdilator 500, and handle portion 200. As the inner dilator 400 isadvanced over the trocar 100, the inner dilator 400 is positionallymaintained relative to the target surface by the trocar 100 with theinner surface of the inner dilator 400 slidably engaging with the outersurface 106A of the trocar 100. Likewise, as the outer dilator 500 isadvanced over the inner dilator 400, the outer dilator 500 ispositionally maintained relative to the target surface by the innerdilator 400 with the inner surface of the outer dilator 500 slidablyengaging with the outer surface 404A of the inner dilator 400. Once theouter dilator 500 is advanced and engaged with the target surface, boththe inner dilator 400 and the trocar 100 may be removed from the tissuedilation system “D” to allow for placement of a pedicle screw at thetarget surface via the outer dilator 500.

While a tissue dilation procedure has been described in terms ofsequential placement of an inner dilator 400 and outer dilator 500 overa trocar 100 toward a target surface, it is contemplated that, dependingon the circumstances of the dilation procedure, the trocar 100 may becombined with the inner dilator 400, the inner dilator may be combinedwith the outer dilator 500, or the trocar 100, the inner dilator 400,and the outer dilator 500 may all be combined prior to advancementthrough tissue toward a target surface during the dilation procedure.

Referring now to FIG. 10 , the trocar 100 is shown in combination withthe inner dilator 400. During combination of the trocar 100 the innerdilator 400, the inner dilator 400 is advanced over the trocar 100,thereby displacing tissue as the inner dilator 400 is advanced toward atarget surface. The inner dilator 400 may further be engaged at thereceiving portion 402 with a surgical tool (not shown) during thedilation procedure. The inner dilator 400 includes a tubular member 404with the bore 408 dimensioned to pass over the trocar 100, and an outersurface 404A dimensioned to slidably engage with inner surface of theouter dilator 500 (see FIG. 7 ) therealong. The inner dilator 400further includes a tapered surface 406 which is dimensioned to engagethe distal region 116 of the trocar 100 (see FIG. 11 ).

Referring now to FIG. 11 , the distal region of the inner dilator 400includes an inner dilator end 406A dimensioned to abut a tapered surfaceflange 108A of the trocar 100. The inner dilator end 406A is located atthe proximal-most region of the inner dilator 400 and comes into contactwith the tapered surface flange 108A of the trocar 100 as the innerdilator 400 is advanced toward the target surface. Contact between thetapered surface flange 108A and the inner dilator end 406A limits distaladvancement of the inner dilator 400 through tissue toward the targetsurface. It is contemplated that, in alternative embodiments, thetapered surface flange 108A of the trocar 100 may be dimensioned so asto allow the inner dilator 400 to advance toward the target surface.Additionally, the inner dilator 400 may have an inner dilator end 406Awhich is serrated for engaging with bone at a target surface.

Referring to FIGS. 12-13 , the trocar 100 is shown in combination withthe inner dilator 400 of FIG. 10 . The bore 118 of the trocar 100, asshown in FIG. 13 , defines a lumen therethrough within the trocar 100.

Referring to FIG. 14 , the handle portion 200, trocar 100 and innerdilator 400 are shown separated from the outer dilator 500. In anembodiment of the present disclosure, after the outer dilator 500 isadvanced toward the target surface and secured via serrated edge 508 totarget tissue, the inner dilator 400 and trocar 100 may be removed fromthe tissue dilation system “D”, with the outer dilator 500 remainingconnected to target tissue at the target surface. To remove the innerdilator and the trocar 100, a clinician may grip the handle member 202of the handle portion 200 and apply force proximally relative to thetarget surface to remove the trocar 100. A step (not shown) is locatedat a distal end of the trocar 100 that engages the inner dilator 400such that the trocar 100 and inner dilator 400 can be removed together.Alternatively, the clinician may apply pressure proximally to theflanges 502 of the outer dilator 500, thereby maintaining pressureagainst the outer dilator 500 and preventing dislodgement of the outerdilator 500 from the target surface as the inner dilator 400 and trocar100 are removed from the tissue dilation system “D”.

Referring to FIGS. 15-18 , a retractor assembly 600 may be slidablyinserted into the bore 518 of the outer dilator 500 to advance a screw“S” toward a target surface. The retractor assembly 600 includes a screwinserter assembly 604, a knob 602, a retractor collar 608, a retractor610, and a screw “S”.

The knob 602 may include one or more flanges for a clinician to gripduring the placement of a screw “S”. It is contemplated that the knob602 may be replaced with a variety of alternative rotational forceapplication mechanisms, designs of which will be apparent to one skilledin the art. The knob 602 is located in a proximal region 614 of thescrew inserter assembly 604 and is dimensioned to receive handle portion200 (see FIG. 4 ) thereon.

The screw inserter assembly 604 may further include one or more openings606 located along its surface. The openings 606 may be selectivelylocated so as to promote engagement with varying surgical instruments(not shown) during the dilation and a screw “S” placement procedure. Thescrew inserter assembly 604 is dimensioned to be slidably assembled withthe retractor collar 608 and the retractor 610. The retractor collar 608may further be dimensioned to enclose a proximal region of the retractor610, thereby preventing maintaining blades of the retractor 610 in afixed position.

For a detailed description of a retractor assembly 600, reference may bemade to U.S. Pat. No. 8,246,538 entitled “Minimally Invasive Retractorwith Separable Blades and Method of Use,” and U.S. Pat. No. 8,734,338entitled “Minimally Invasive retractor and Methods of Use,” the entiredisclosures of which are incorporated herein by reference.

Referring to FIG. 15 , the retractor assembly 600 is shown incombination with an outer dilator 500 (see FIG. 7 ). A retractor collar608 is dimensioned to abut flange 502 for selective detachment of theretractor 610 from the retractor collar 608 as the retractor assembly600 is advanced toward the target surface. It is contemplated that theretractor collar 608 may be dimensioned so as to be slidably insertedinto the bore 518 of the outer dilator 500 while advancing the retractorassembly 600 toward the target surface. The retractor collar 608 furtherincludes an inner surface 608A and an outer surface 608B, with the innersurface 608A being dimensioned to receive a retractor 610 duringassembly therein (see FIG. 19 ).

Referring to FIG. 16 , in use the retractor assembly 600 is advancedthrough a bore 518 of the outer dilator 500, with the outer dilator 500being fixed to a target surface. Prior to insertion, the clinicianassembles screw “S” to the distal region of the screw inserter assembly604. During assembly, the clinician slides the retractor 610 over thescrew “S” and the screw inserter assembly 604, thereby advancing theretractor 610 toward the proximal region of the retractor assembly 600.The clinician also attaches knob 602 to the retractor assembly 600. Incombination, the clinician may advance the retractor assembly 600through the bore 518 of the outer dilator 500 advancing from theproximal region of the outer dilator 500 to the distal region of theouter dilator 500 toward a target surface.

Referring to FIGS. 17-20 , the retractor assembly 600 is shown incombination with the outer dilator 500. In a contemplated embodiment,upon assembly the retractor collar 608 secures the proximal portion ofthe retractor assembly 600 along a proximal region of the bore 518 ofouter dilator 500. Additionally, the screw “S” may be engaged by anengagement portion 618 of the screw inserter assembly 604 (see FIG. 20), with both the screw inserter assembly 604 and screw “S” providingoutward force to secure the retractor 610 at a distal region of the bore518 of the outer dilator 500 therein.

Referring to FIG. 19 , the retractor collar 608 includes a distal collarsurface 608F which, when combined with the retractor assembly 600 (seeFIG. 15 ) abuts flange 502 of the outer dilator 500. As a clinicianadvances the retractor assembly 600 beyond a predetermined point, theclinician may dislodge the retractor 610 from the retractor collar 608.Once dislodged, the retractor collar 608 may maintain position in thebore 518 of the outer dilator 500 to stabilize the retractor assembly600 as the retractor assembly 600 is advanced toward the target surface.To remove the outer dilator 500 from the surgical site, the clinicianmay apply force proximal relative to the target surface to dislodge theouter dilator 500 from the target surface.

Referring to FIG. 20 , engagement portion 618 may further includeengagement tip 618A dimensioned to engage screw head 616A. As a resultof the mating of the engagement tip 618A with the screw head 616A,rotation of the screw inserter assembly 604 rotates the screw “S” forinsertion into or removal from target tissue (i.e., bone). After placingthe screw “S” into target tissue, the clinician may apply sufficientforce to screw inserter assembly 604 proximally or away from screw “S”to the screw inserter assembly 604, thereby dislodging the screwinserter assembly 604 from the screw “S” and the retractor 610. If theclinician determines it necessary to remove screw inserter assembly 604while leaving retractor 610 in position, the surgeon may apply force asis necessary to dislodge the screw inserter assembly 604 from theretractor collar 608, thereby maintaining the position of the retractorcollar 608 and the retractor 610, relative to screw “S”.

With continued reference to FIG. 20 , a distal region 620 of theretractor 610 may be shaped so as to require force to dislodge theretractor 610 from the screw “S”. Upon removal of the screw inserterassembly 604, the retractor 610 may contract around the screw head 616A.It is contemplated that retractor 610 may be made of a pliable,biocompatible, and sterilizable material such as polypropylene,polyethylene, or polycarbonate. By including pliable, biocompatible, andsterilizable materials, the retractor 610 may be deformed at the distalretractor end 620 as the retractor 610 is slid over the screw head 616A.

Referring to FIG. 21 , the retractor collar 608 is illustrated,including an outer collar surface 608B, an inner surface 608A, a distalcollar surface 608F, and collar flanges 608D. Upon insertion into theretractor 610, the proximal region of retractor 610 may be pressedagainst the distal collar surface 608F. The inner surface 608A therebyprevents retractor 610 from separating along retractor seams (not shown)during the surgical dilation procedure. The collar flanges 608D aredimensioned to be received by the proximal region of the retractor 610prior to insertion into the tissue dilation system “D”. The collarflanges 608D may include a tapered surface 608E which facilitatesassembly of the retractor 610 and the retractor collar 608 during thedilation procedure, as is necessary.

Referring to FIGS. 22-25 , another embodiment of an outer dilator isillustrated as outer dilator 500′ and may include an outer tubularmember 504′, an inner tubular member surface 512′, flange 502′, and atapered surface 506′. The flanges 502′ may further include an openings514 dimensioned to receive a temporary fixation pin 700 (see FIGS. 26A,26B). The outer dilator 500′ may further include one or more cavities516 located along the outer tubular member 504′, each cavity 516dimensioned to receive at least a portion of temporary fixation pin 700therealong. Additionally, protrusion 522 may be located along the outertubular member 504′ and may partially or fully enclose each cavity 516,thereby preventing the temporary fixation pin 700 from moving laterallyrelative to outer dilator 500′ while guiding longitudinal movement ofthe temporary fixation pin 700.

Referring to FIGS. 26A-26B, the temporary fixation pin 700 may include arecess 702, a proximal region 704, a tubular member 706, threads 708,and a tip 710. The recess 702 may be located in a proximal region of thetemporary fixation pin 700. The recess 702, as illustrated in FIG. 26Bhas a hexalobular shape, which permits engagement with a surgical tool,providing increased grip for application of rotational force totemporary fixation pin 700. It will be apparent to one skilled in theart that recess 702 may be shaped in a variety of different ways whichpermit precise transfer of rotational force from a surgical instrument(not shown) while reducing the chance of stripping the recess 702 duringinstallation and removal.

With continued reference to FIG. 26A, a tubular member 706 traverses thelongitudinal axis A-A, connecting a proximal region 704 to threads 708and a temporary fixation pin tip 710.

Referring to FIG. 27 , another embodiment of an outer dilator isillustrated as outer dilator 500″ and may include an outer tubularmember 504″, an inner tubular member surface 512″, flange 502″, and atapered surface 506″. The flanges 502″ further include openings 514″dimensioned to receive a temporary fixation pin 700 (see FIGS. 26A, 26B)therethrough. The temporary fixation pin 700 of FIGS. 26A-26B iscombined with outer dilator 500″. During installation, the tip 710 maybe advanced through the proximal region of outer dilator 500′ throughopening 514″ located on flange 502″. The temporary fixation pin 700 maysubsequently be advanced along longitudinal axis A-A to be engaged withthe target surface. After assembly, the temporary fixation pin 700 maymaintain force against flange 502″, thereby providing additional forceagainst outer dilator 500″, fixing outer dilator 500″ to target tissue.

It is contemplated that a kit may be provided including the tissuedilation system “D” as disclosed herein. Additionally, a kit may includethe retractor system 600 as described herein, either combined with thetissue dilation system “D” or as a stand-alone kit. In alternative kits,outer dilator 500′ and/or outer dilator 500″ may be included separately,or in combination with one or more temporary fixation pins 700, innerdilator 400, trocar 100, and/or handle portion 200. It is alsocontemplated that temporary fixation pins 700 may be included in aseparate kit. Additional tools which may be useful for a clinicianduring the dilation procedure may be included in the described kits. Thekits described in the present disclosure may be provided with sterilepackaging to facilitate opening and immediate use in a sterileenvironment such as an operating room.

Any of the components presently disclosed may be formed of any suitablebiocompatible material which is of sufficient strength to receive boththe longitudinal and rotational forces necessary for the proceduresdescribed. It is contemplated that the disclosed devices may be made ofmaterials including, but not limited to, titanium, titanium alloys,stainless steel, cobalt chrome, and nickel titanium or polymercompositions.

Persons skilled in the art will understand that the structures andmethods specifically described herein and shown in the accompanyingfigures are non-limiting exemplary embodiments, and that thedescription, disclosure, and figures should be construed merely asexemplary of particular embodiments. It is to be further understood thatthe present disclosure is not limited to the precise embodimentsdescribed, and that various other changes and modifications may beeffected by one skilled in the art without departing from the scope orspirit of the disclosure. Additionally, the elements and features shownor described in connection with certain embodiments may be combined withthe elements and features of certain other embodiments without departingfrom the scope of the present disclosure, and that such modificationsand variations are also included within the scope of the presentdisclosure, and that such modifications and variations are also includedwithin the scope of the present disclosure. Accordingly, the subjectmatter of the present disclosure is not limited to what has beenparticularly shown and described.

The invention claimed is:
 1. A tissue dilation system comprising: atrocar having an elongated body with a bore extending therethrough, adistal region of the elongated body having an engagement member foranchoring into bone and including a handle portion configured to beremovably attached to the trocar; a stylet insertable into the bore andconfigured to threadably couple with the handle portion; and a firstdilator having an elongated body and translatable over an outer surfaceof the trocar.
 2. The tissue dilation system of claim 1, wherein theengagement member of the trocar includes a helical thread for anchoringinto bone.
 3. The tissue dilation system of claim 1, wherein the styletis configured such that a distal region of the stylet extends distallybeyond the distal region of the trocar when the stylet is threadablycoupled with the handle portion.
 4. The tissue dilation system of claim1, further including a retractor assembly including a pedicle screw, aretractor, a screw inserter, and a collar; wherein a distal end of theretractor is coupled to the pedicle screw such that the retractorextends proximally from the pedicle screw; wherein a distal end of thescrew inserter is engageable with the pedicle screw while being receivedwithin the retractor so as to advance the pedicle screw into bone; andwherein the collar is configured to stabilize a proximal region of theretractor with respect to the screw inserter.
 5. The tissue dilationsystem of claim 4, wherein the collar has a tapered distal endconfigured to be inserted into the proximal region of the retractor. 6.The tissue dilation system of claim 4, further including an outerdilator having an elongated body that is translatable over an outersurface of the first dilator, the outer dilator being configured toreceive the retractor assembly therein as the retractor assemblyadvances distally relative to the outer dilator.
 7. A method fordilating tissue comprising: inserting a stylet into a bore that extendsthrough a trocar between proximal and distal regions thereof, such thata distal region of the stylet extends beyond the distal region of thetrocar; engaging a target surface of a bone with the distal region ofthe trocar so as to anchor the trocar into the bone at the targetsurface; removing the stylet from the bore of the trocar; andtranslating a first dilator over the trocar towards the bone at thetarget surface.
 8. The method of claim 7, further including removablyattaching a handle to the trocar.
 9. The method of claim 8, furtherincluding detachably securing the stylet to the handle.
 10. The methodof claim 7, further including removing the trocar from the targetsurface.
 11. The method of claim 7, further including translating anouter dilator towards the bone at the target surface while the firstdilator is received within a bore of the outer dilator.
 12. The methodof claim 11, further including removing the first dilator from the boreof the outer dilator after the step of translating the outer dilatortowards the bone.
 13. The method of claim 11, further includingadvancing a pedicle screw into the bore of the outer dilator andanchoring the pedicle screw to the bone at the target surface, thepedicle screw having a distal end of a retractor coupled thereto suchthat the retractor extends proximally from the pedicle screw, theretractor defined by first and second longitudinal blades spaced apartfrom one another.
 14. The method of claim 13, wherein the steps ofadvancing and anchoring the pedicle screw are performed with a screwinserter engaged with the pedicle screw while the screw inserter isreceived within the retractor and while a collar is connected to aproximal region of the retractor so as to stabilize the first and secondblades at the proximal region of the retractor.
 15. The method of claim14, further including inserting a tapered distal end of the collar intothe proximal region of the retractor.
 16. The method of claim 14,wherein the step of advancing the pedicle screw into the bore of theouter dilator includes the collar moving into engagement with a proximalend of the outer dilator during advancement of the pedicle screw and theretractor, so as to cause the collar to disconnect from the proximalregion of the retractor.
 17. A method for dilating tissue comprising:inserting a stylet into a bore that extends through a trocar betweenproximal and distal regions thereof, such that a distal region of thestylet extends beyond the distal region of the trocar; engaging a targetsurface of a bone with the distal region of the trocar; removing thestylet from the bore of the trocar; translating a first dilator over thetrocar towards the bone at the target surface so that the first dilatoris received within a bore of an outer dilator; and translating the outerdilator towards the bone at the target surface while the first dilatoris received within a bore of the outer dilator, wherein translating thefirst dilator and the outer dilator towards the bone occursimultaneously.